Adventures in music: Creating & Playing a totally new (and better) musical instrument: the jammer.

Jun 10, 2012

An inexpensive, simple, but effective choral shell

How to build a simple yet very effective choral shell for $400.

The community based show-chorus I sing with, the Maple Leaf Singers, wanted to do something to improve the sound of our performance for our big fund-raising show - we sing over 15 times per year, but just a pair of shows bring in our critical revenue.

Massey Theatre, the place hosting the big shows, is a big box of a place, with a huge backstage and theatrical fly system. Our singing vanishes into the void, and we tend to yell because the sound balance is off - we can't hear each other. Yelling is not good and lowers our pitch, yet the audience despite our being miked to the limits of feedback, still can't hear us well.

The current option of choice - miking every performer - is not an option for a 60-member group. Nor is changing the venue. In desperation we decided to try sound reflectors, and to my modest surprise (I'm always surprised when something I build succeeds) - it worked better than we had hoped.

Consulting the local experts

First here's what researching with the local theatre people - the ones we consider to be keeners at their craft.They told us that a shell would do nothing for the audience, but would help us hear each other. This alerted us as to what to expect default, so that we weren't disappointed and could design around the default limits.

What our goals were

We wanted to, in decreasing importance:

1. Have the audience hear us - well duh! but today's audience wants volume

2. Hear each other - often taken for granted

3 Hear our monitors- without feedback

4 Hear the audience - this last is what makes it fun!

Studying the shapes of the commercial units, it turns out that a traditional choral shell - costing thousands of dollars and weighing many pounds, does not reflect the sound evenly - by design it scatters it within the choir, so that it primarily supports objective #2.

With modern materials, it seemed might be possible to satisfy more of the objectives, by focusing the sound at the audience, and by "piping" it from one side of the chorus to the other.

So what we built

Our choral shell system has two components, one not very visible, the other very much so. Both are made of the material Coroplast, the lightweight material using to make signs.

1. The invisible - but important! - black railing cover of coroplast

We now use this for all performances, as it is easy to set up and gives us consistent sound

2. The visible white shell, flown by the theatre system

This is only for use at the big theatre, directing some sound to the audience and some audience sound to us.

Note that it also acted as a "sonic pipe", transfering sound from riser-left to riser-right and vice-versa.

What it looks like: one segment, front and back:

I used 3 thin wires to bend the panel.

What it looked like in practice, with the segments all linked together with Velcro, flown and lit:

The wonderful Massey staff were keen to try it, and suggest improvements.

Results

The choral shell was very effective in a number of ways, and seemed to have no downside:

The intra-choral sound was excellent: we could hear each other, didn’t yell, stayed on pitch, and could dis-regard monitors that were too loud or too quiet

The shell apparently focused the audience attention on the choir, making us look closer and more intimate

We could hear the audience a bit better; they sounded closer

We had remarks like “Wow, you guys really had a lot of very difficult harmonies this year!”

I think he choir most benefited – no-one’s voice was hoarse after 3 days of singing - the first time ever.

Our pitch was good: I know that the piano/track never sounded sharp and our chorister with perfect pitch reports it was good

The effect was like singing in the our normal rehearsal hall, perhaps with an even better unit sound - I could hear the ladies on either side and felt a solid crisp group sound. |

and the cost was low - $400 for 10 sheets of Coroplast, lots of Velcro, and some wood.

SO if you are interested, let me know, and I'll post details of how to make your own.

Ken Rushton.

* The Massey Staff also borrowed a new high-grade overhead microphone that helped.

Comments

Thanks for your info. Making some kind of shells has been on my mind for a bit since we have a perfect way to permanently mount them on the back wall of the choir loft in our church.
Weight and portability is not an issue, so I'm wondering what would be the best choice of material for acoustics? We could use plywood and even sandwich (double it) with space in between say 4" so it would be hollow. I would appreciate any thoughts you would have on this.
Thanks, Dan

We have five 4-step Wenger risers, which set up in an arc, so we needed a curved shell. So, we supported each of the “flying” sheets individually, so we could position each one separately behind the risers.

We supported the shell pieces with lighting stands (ADJ LTS-2 – http://www.adj.com/lts-2). These stands are rated to 80 lbs and extend up to 12 ft. We needed 5 of them and the total cost was ~$650 CDN ($109/each plus taxes and shipping).

The cross bars are 4 ft long and come with 4 bolts with wing nuts. We replaced the bolts with longer ones and bolted 7 ft long pieces of 1x4 to the cross members. We attached the flying shell pieces to the cross members with ¾ inch Velcro (3 18” strips per shell fragment).

The shell fragments were 4x8 pieces of coroplast. We put the Velcro strips slightly lower then midway (18” up from the bottom).

The other change we made was how we established the curve on each shell piece. We cut 1” slots @ 1ft intervals along both top and bottom edges of the shell pieces. We tied lengths of heavy fishing line (actually whipper snipper cord from a long deceased whipper snipper) into 44” lengths with knots at both ends and washers inside the knots. To create the curve you simply slip one end of the cord into a slot (with the washers at the back) then slip the other end of the cord into the matching slot on the far side of the coroplast sheet. These are easy to assemble and take apart.

It’s a bit tricky to get the length between the washers consistent. I tied a knot on the end of my roll of cord, cut the cord longer than needed and slid on both washers. Then I measured the 44” and marked the cord with a magic marker. Then I used that mark to locate the second knot. The mark needs to be just on the straight cord in front of the finished knot.

We tried several distances between cords and found that with 24” spacing the top edge of the shell had a bit of a wave between cords, but with 12” spacing the top edge of the shell was nice and straight.

Our total costs were $1300. All our costs were consistent with yours with the marked addition of the lighting stands. However we now have a sound shell with which the choir is totally pleased and which should last us for years.

I serve as stage manager for The Palmetto Mastersingers in Columbia, SC. I would love to have a look at plans for your design. Do your plans allow for support of these curved panels from the ground instead of suspended from the ceiling? We have 3 level, 32'x12' risers when fully assembled. We would also require some sort of black panels to attach to the back of our risers for the area below the curved panels. Thousands of dollars for a shell is way out of budget for a volunteer non-profit group like us. We number anywhere from 50 to 80 singers depending on the year.

Dear Ken: If I could have the plans, it would be a godsend for the very small HS Choir I am directing in two weeks for our Spring Concert, in a barn of church, and with an Admin that won't/can't see the necessity of actually amplifying a choir for the audience's sake, as well as for the students!

I may be a bit late with this ... but could you tell me the thickness of the 'coroplast' you used? We here[Australia] have the option of, e.g: 5mm or 3mm. I think the thicker the better, both for rigidity & sound reflection ... what is your view, please?

From your posting I assume you are retired now - as am I. I have been asked to build acoustic shells for our church choir and this seems to be the most effective, lightest, storable and inexpensive method available.

Ken-
I am SO interested in getting all the details to build this type of shell. I teach music at a small elementary school. The building is very old, and the only "stage" is on one end of a sunken gym. Basically, there are big wooden doors that can be opened and a railing at the front of the doorway so audience could sit in chairs down on the gym floor and the kids could perform up behind the rail. Only problem is that they would be standing in a main hallway. We need a way to make a "back" to our stage to block sound and sight lines down that hall. Please help! :)

Sorry!
I am unable to do any major postings until Jan 6, when I retire to specialize in:
1. learning to play my jammer.
2. post fun things about Music.
I promise that I will post all that I know about the choral shell in January. I will finally have time to do so.

A tip for the meantime: I created 8" high riser step covers from coroplast. These were very successful.
The boost reflected sound and the stopping of sound sneaking around the back of the risers and making the sound muddy made it easier to hear each other and the audience seemed to like it.
Just take careful care that the feet can't catch on a protruding piece of plastic.
Ken.

I too would like to hear the information regarding your homemade choral shell. We too have a multi-purpose gymnasium that we use for concerts and we desperately need a shell. Thanks Ken for any information and help!

Hello all.
I'm unable to post a long reply to your pleas, as it's show season. I tried making a video, several months ago, showing how I bend and fly the upper shell, but I learned that (1) videos are very time consuming. and (2) that I didn't have (or make) the time needed to do it - I kept doing a bit, getting interrupted, restarting - you doubtless know the drill. Instead, here are some notes:

First, put up the black railing cover over the back of the risers. This is cheap and easy to do. I presume you currently have black curtains stuck on with velcro? If so, this is easy:

- put the 8' x 4' sheets coroplast against the railing, and trim it to the height of the railing (save the trimmings).
- Cut the sheets down from 8' long to exactly 4'
- Protect yourselves against plastic-caused "paper cuts" by wrapping black electrical tape over the top edge.
- then stick 1/2 inch squares of velcro on the back side of the plastic sheets, about one per every 8-12 inches. Don't use too much, or the coroplast will be stuck on so tightly that you will bend it when you pull it off.
- If you don't already have velcro on the back railing, buy enough velcro to cover the top bar,
clean it carefully with solvent or a good detergent, and stick the velcro on securely.
- To speed up setup, put an big "arrow" on the back-side of the sheets pointing to the top edge.
This is a big help.

Extra tip: to make the sheets easier to handle and store, suggest drilling a thumb-size (1 inch or so) hole in the top centre of the sheets, to give them a grip, and put a 1/2 inch square of velcro on all 4 corners, so that the stacked sheet layers would stick together and can be put in the truck easily.

Hello Ken,
I have been researching exactly what you did for your music shells. Our Chorale does fund raisers for not for profit organizations in the area. Purchasing shells is cost prohibitive because we rely on only donations from business to supply music and stipends to the few musicians we have to hire for our two to three concerts per year. If you could send more detailed information on your construction technique it would be very valuable, in particular the method of securing the wire to the material without tearing or breaking it. Also we do not have the luxury of flying them and have to stand them up on the stage flooring. Any ideas for this would also be helpful. Thank you for any information you could supply,
Fran Marien

I sure hope this is still active! I would absolutely LOVE to get the details on building this shell and/or a portable one like others mentioned. I teach at a K-8 school that doesn't have the thousands necessary for a shell, but this could do some GREAT things for us!

I just built a double-size one and have simplified the design, taking pictures and movies as I went. I hope to squeeze the time to document and post the details this week-end.
I know I've missed on my promises to do so in the past, but hopefully the time-stealing demons will hold off for a few days.
Ken.